The proposed work follows the lines of development mentioned in the progress report: (1) Induced polydipsia in rats shows many of the properties of an opponent-process system. We are now testing the effects of food stimuli at different points in the taste preference hierarchy: The higher is the preference for a taste, the easier it should be to induce polydipsia with long interstimulus intervals. We are now pushing ahead with our tests of Siegel's interpretation of tolerance as a conditioning phenomenon rather than a non-associative opponent-process. We are having difficulty replicating Siegel's findings and have developed an elaborate technology to remove the artifacts in his work. We are proceeding with our work on social attachment in chicks and ducklings, testing the interactions between affective states generated by fearful objects and objects of social attachment. Finally, we are studying the effects of interrupted meals in rats on total food intake, testing the notion that the opponent-process for taste decays quickly.